Parison prepinching and preblowing apparatus



Feb. 4, 1969 T. 1. NAVE ETAL 3,425,090

PARISON PREPINCHING AND PREBLQWING APPARATUS /N VE N TORS T. J. NAVE M.E. LARKIN q #MBU W7C? j Arron/vars PARISON PREPINCHING AND PREBLOWINGAPPARATUS Filed April 4. 1966 Feb. 4, 1969 T. 1. NAVE ETAL l Sheet..lllllllll /NvE/vrons T. J. NAVE M. E. LARKIN VWM? MQW?? A T'TORNE YSFeb. 4, 1969 T. J. NAVE ETAL 3,425,090

PARISON PREPINCHING AND PREBLOWNG APPARATUS Filed April 4, 196e sheet 3of s EXHAUST F/G 3 /NyE/vrons T. J. NAVE By M. E. LARKIN www3 A 7'TURA/EVS United States Patent O 7 Claims This invention relates to anapparatus for prepinching and preblowing a parison. This invention alsorelates to apparatus for controlling the prepinching and preblowing oftheparison.

Heretofore, when blow molding articles which have remote corners, e.g.,hollow rectangular containers, the parison upon blowing in the mold camein contact with the sides of the molds before reaching the remotecorners. The results of such an operation were an article having undulythin and weakened corners.

It has been found that undue parison thinning in remote corners of themolds can be counteracted if the parison is prepinched to close off itslower end and make it substantially air-tight. Low pressure fluid, e.g.,air, is then introduced into the prepinched parison to preblow theparison, i.e., balloon the parison (partially stretch), to increase theinternal volume of the parison at least volume percent or the internaldiameter of the parison at least 5 percent so that when the preblownparison is placed in the mold it is already directed towards the remotecorners of the molds and the resulting product had a more Iuniform wallthickness even at these remote corners.

In many cases the articles formed by a particular blow molding processmust be carefully controlled to fall within very narrow weight limitsand -whenever these limits are exceeded the article is of no use and hasto be discarded. Further, in many cases the prepinched parison isruptured by the preblowing air which rendered the parison unless forblow molding.

It has also been found that the reproducible weight and preblow ruptureproblems can be obviated and a blow molded article having substantiallyuniform wall thickness even at remote corners still formed by a precisecorrelation of the prepinching and preblowing operations.

According to this invention there is provided an apparatus forprep-inching and preblowing a parison while continuously anduninterruptedly forming that parison and with substantially no rupturingof the preblown parison and with no substantial weight variation betweenblow molded articles, by forming a first length of an open ended parisonin a conventional manner, pinching the parison, preblowing the parison,and then blow molding the preblown parison. To assure against preblowrupture, the prepinched parison can be further formed into a secondlonger length so that the parison -Will have an internal 'volume abovethe prepinohed area suicient to receive the preblowing uid withoutrupturing and only then admitting preblowing fluid tothe interior of theprepinched parison. Thus, by this latter aspect no preblow fluid entersthe parison during pinching thereof or for a finite time period aftersuch pinching.

The prepinching apparatus of this invention includes a pair of opposedypinch members each rotatably carried on at least one gear means, thegear means for each of the pinch members being meshed with one anotherand one of these gear means also being meshed with a separate gearmeans. There is also provided means for moving the separate gear meansso as to cause rotation of the pinchmember carrying gear means in eithera clockwise or counter clockwise manner and the resultant movement ofthe pinch members towards or away from one another ICC depending uponthe direction of movement of the separate gear means.

The control apparatus of this invention employs an accumulator forsupplying parison material to the parison forming means, e.g., anextrusion die, means for moving parison material from the accumulator,and rst and second switch means adjacent the means for moving materialfrom the accumulator. An actuating means is carried by the means formoving material from the accumulator and adapted to actuate the firstand second switch means. Means is provided for moving the mold parts andthis means is connected to the first switch means. A valve means isconnected to a fluid operated means which carries the separate gearmeans that operates the pinch members, the valve means being adapted topass uid into the fluid operated means to cause the pinch members tomove towards one another and also to pass uid into the fluid operatedmeans to cause the pinch members to move away from one another and tocause at substantially the same time preblowing fluid to pass throughthe parison being formed. A time delay means is connected between theswitch means and the valve. A norm-ally closed, second valve isconnected to the conduit for carrying preblow fluid to the parison. Athird switch means is adapted to be actuated when the molds are movedinto the open position and in turn to open the normally closed secondvalve to allow preblow uid to pass into the parison. A fluid delay meansdownstream from the second valve is employed to delay the passage ofpreblow uid into the parison for a finite time suicient to allow theformation of a parison of sufficient internal volume to contain thepreblow fluid without rupturing.

Accordingly, it is an object of this invention to provide a new andimproved apparatus for prepinching and preblowing parisons. It isanother object of this invention to provide a new and improved controlapparatus for controlling the prepinching and preblowing operations in aprecise sequence of events.

Other aspects, objects and the several advantages of this invention willbe apparent to those skilled in the art from the description, drawings,and appended claims.

FIGURE 1 shows a top view of prepinching apparatus according to thisinvention.

FIGURE 2 shows a cross section of the apparatus of FIGURE 1.

FIGURE 3 shows a system embodying the control aspect of this invention.

In FIGURE l there is shown pinch bars 1 and 2 carried on arms 3 through6 which arms are attached to circular gears 7 through 10'. Gears 7 and8` and gears 9 and 10* are meshed with one another. Gear 8 is alsomeshed with rack 11, rack 11 being connected to the piston rod ofhydraulic cylinder 12.

Thus, when the piston of cylinder 12 is moved upwardly or downwardlyrack 11 is also moved and therefore rotates gear 8. The rotation of gear8 causes the rotation of gears 7, 9, and 10l thereby causing bars 1 and2 to move towards or away from one another depending upon the directionof movement of rack 11.

FIGURE 2 shows a Cros-s section of the apparatus of FIGURE l includingpiston rod 13 of cylinder 12. Cylinder 12 can be pneumatic, hydraulic,electrical, or any conventional actuating means. Arm 3 is also shown tocarry a member 14 which extends along the length of bar =1 and whoselength can be substantially shorter than or equal to the length ofbar 1. Member 14 acts as a molded article ejection member in that itextends downwardly far enough to come in contact with that portion ofthe parison that sticks above the molds after the molding operation iscompleted and therefore pushes the molded article out of the mold whenthe pinch bars are moved towards one another. The actuation of the pinchmembers to eject the molded article can be accomplished manually or canbe programmed into the automatic controls in a manner obvious to oneskilled in the art, e.g. mold half 22 can trip a microswitch as it movesaway from mold half 23 after completion of the molding operation, thetripping of the microswitch causing immediate activation anddeactivation of cylinder 12, the activation being sufcient to just causearm 3 to move .past mold 22 without going through the whole pinchingcycle.

Bars 1 and 2 can be coated with a suitable material which preventssticking of the bars to the heated parison, a preferred material beingpolydimethylsilicone.

In the operation of the apparatus of FIGURE l or 2 to cause pinching ofthe parison by movement of bars 1 and 2 towards one another, preferablysubstantially into a contacting relationship with one another, thepiston in cylinder 12 is actuated such as by passing high pressure airinto the top of the cylinder above the piston thereby causing piston rod13 and rack 11 to move downwardly. This movement of rack 11 causes gear8 to rotate clockwise and gear 7 to rotate counter clockwise therebyswinging arms 3 and 4 towards one another. When in its lowermostposition rack l11 can be retracted to reverse the movement of bars 1 and2 by passing air under pressure into the bottom of cylinder 12 below thepiston therein or by employing a spring biased piston which willautomatically return to its uppermost position when the high pressureair is removed from the top portion of cylinder 12.

FIGURE 3 shows an extruder die 20 from which is issuing a hollowcylindrical parison 21. The apparatus of FIGURES l and 2 is orientedwith respect to die 20 and parison 21 in the manner shown so that bars 1and 2 will meet below -die but above molds 22 and 23 so that a portion24 of the parison can extend below bars 1 and 2 when pinching theparison. The length 24 of parison 21 is necessary in order to achievesatisfactory sealing, e.g. heat sealing, of the bottom of the parison tomake airtight the interior of the parison that extends above the pinchedportion. Conduit 25 extends into the interior of die 20 so as to providepreblowing air for parison 21.

Die 20 is operatively connected through conduit 26 to an accumulator 27having therein a piston 28 whose supporting rod 29 extends exteriorly ofthe accumulator. Material, e.g., thermoplastic, from which the parisonis formed is supplied to accumulator 27 from conventional extruder 30(not all shown) through conduit 31.

Piston rod 29 is actuated by a conventional actuating means which can bea hydraulic, pneumatic, or other conventionally operated cylinder.However, it is necessary that actuator 35 be adapted to allow theretraction of piston 28 under the force of material entering accumulator27 from conduit 31.

Piston rod 29 carries an actuating arm 36 which is adapted to contactswitches 37 and 38 and trip same. Switch 38 is operatively connectedthrough electrical conduit 39 to motor 40 which moves molds 22 and 23towards one another for a blow molding operation. The apparatus forcontrolling the movement of the molds through the molding cycle isconventional and therefore not shown.

Switch 37 is operatively connected through electrical conduit 4'1 to aconventional electrical delay timer 42. A suitable delay timer is thatmarketed by the Eagle Signal Company of Davenport, Iowa. The delay timeremployed should be adapted to receive a signal from switch 37, pause anite length of time before switching itself to the on position, and thenpause another iinite length of time after switching itself to the onposition before switching itself oif and resetting itself to awaitanother signal from switch 37.

Delay timer 42 is operatively connected through electrical conduit 43 tofour-way, solenoid operated, automatic spring return, valve 44. Valve 44is operated by air from conduit 45, a suitable air pressure beingconventional plant pressure, i.e., on the order 0f from about 100 toabout p.s.i.g. Valve 44 is spring biased so as to be normally in aposition which causes air from 45 to pass through conduit 46 and intoconduits 47 and 48.

The air passing through conduit 47 passes into the bottom of cylinder 12thereby forcing the piston in that cylinder and rack 11 into theuppermost position. The uppermost position also maintains pinch bars 1and 2 in their open, non-pinching position. The air in 48 passes tonormally closed, solenoid operated, spring return, two-way valve 50.

Valve 50 is operated through electrical conduit 51 by microswitch 52which is actuated by the opening of molds 22 and 23. Actuation of switch52 by mold 23 causes the opening of normally closed valve 50 therebyallowing preblow air to pass through line 53 to air delay timer 54. Airdelay timer 54 holds preblow air from passing into conduit 25 for afinite length of time, the finite length of time being determined by theamount of time required to extrude a length of parison above the pointwhere it is pinched so that the internal volume of the parison issufcient to accept the preblow air without rupturing. A suitable airdelay valve is a Timac mechanical valve produced by the Mac ValveCompany of Detroit, Michigan. When the air delay valve 54 times out itpasses the preblow air through line 55 and pressure regulator 56 intoline 25 and therefore preblows the prepinched parison.

In operation, when molds 22 and 23 are closed needle N punctures theparison wall, air under normal blow molding pressure is admitted to theinterior of the preblown parison, and the blow molding operation iscarried out. During the blow molding operation accumulator 27 is lledfrom extruder 30 and piston 28 is pushed back by the material enteringaccumulator 27 from line 31. No preblow air is passed through conduit 25at this time since valve 50 is normally closed.

At the termination of the blow molding operation molds 22 and 23 areopened and the molded article ejected, preferably by actuation ofcylinder \12 by passing air through line 49 thereby causing pinch barsl1 and 2 to come together and ejection arm 14 to hit that portion of theblow molded article that extends above mold 22. Mold 23 tripsmicroswitch 52 which then opens normally closed valve 50 to allowpreblow air to pass through conduit 25 into open bottomed parison 21after air delay valve 54 is timed out.

At about or shortly after the time the preblow air is admitted to line25, accumulator 1 becomes lled with thermoplastic and arm 36 tripsmicroswitch 37. Thus, electrical time delay 42 is actuated. Delay timer42 hesitates a finite period of time which is generally a matter of afew seconds to allow a certain amount of parison 21 to be extruded sothat length 24 of parison 21 extends below the bottom of members 1 and 2when in the pinching position. Delay timer 42 then switches itself tothe on timing position at which time four-way valve 44 is actuated sothat air from line 45 is switched from its normal path through lines 46,47, and 48 to its alternative path where it passes through line 49 tocause the piston in cylinder 12 and rack 11 to move downwardly and causepinch bars 1 and 2 to close and prepinch parison 21. This switching ofvalve 44 cuts off the air from both lines 47 and 48 so that no preblowair passes into the parison while it is being prepinched, therebypreventing rupturing of the parison during or just after prepinching ofsame. When the air in line 48 is cut off air delay valve 54 resetsitself to cause another delay when air is again passed thereinto.

After turning itself to the on position delay timer 42 times out in afraction of a second, generally on the order of about one-tenth of asecond, or just long enough for bars 1 and 2 to prepinch parison 21.When delay timer 42 times out it moves switch 44 back to its normalposition so that lair then passes through conduits 46, 47, and 48thereby causing the piston in cylinder 12 and rack 11 to retract andopen pinch bars 1 and 2 to the position shown in FIGURES 2 and 3. Also,at this time air is again passed through 48, still open valve 5.0, andline 53 into reset air delay valve 54.

Air del-ay 54 stops the flow of air for a few seconds, generally on theorder of 1 to 2 seconds, to allow parison 21 to be extruded further sothat the internal volume of the parison above the prepinch line issufficient to contain the preblow air without rupturing. At the time airdelay 54 times out the volume of parison 21 is sufiiciently large thatit receives the preblow air and is extended thereby prior to closure ofmolds 22 and 23 around the preblown parison.

Just after air delay 54 times out and parison 21 is preblown, arm 36contacts switch 38 to activate motor 40 and cause molds 22 and 23 toclose around tre preblown parison. When mold 23 is moved away fromswitch 52 valve 50 resumes its normal closed position thereby cuttingoff preblow air from line 25. The parison in the mold is then blowmolded in a conventional manner and the cycle -above is repeated.

Generally, the preblow air pressure is regulated by needle valve 56 andthe pressure of the preblow air will vary widely depending upon the wallthickness of the parison, the weight of the blow molded article desired,the particular material from which the parison is formed, thetemperature of the parison, and the like. The pressure of the preblowair or other fluid utilized as la preblowing medium can be in the rangeof from about l to about p.s.i.g., although higher and lower pressurescan be used.

The instant invention is applicable to any formable material but isparticularly applicable to plastic materials such as thermoplastics.Generally, the invention can be practiced on homopolymers and copolymersformed from l-olefins having from 2 to 8 carbon atoms per molecule,inclusive, polyamides, polyesters, polyvinyl alcohol, acrylic polymers,polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, and thelike. The material in accumulator 27 and die 20 will be maintainedsubstantially at the melt extrusion temperature for that material justthe same as if the material were being extruded diretly from extruder30.

Example Polyethylene having a density of 0.96 gram per cubic centimeterat C. and a melt index of 0.2 is extruded at a temperature of about 400C. to produce a hollow cylindrical parison using the apparatus shown inFIG- URE 3. The parison is continuously extruded through die 20 and thestroke of arm 36 is adjusted so that it trips switch 37 and at the sametime piston 28 is moved towards die 20 to extrude parison 21 so that thetime period that elapses between activation of time delay 42 by switch37 and the time at which time delay 42 switches itself to the onposition allows for the extrusion of about 2 inches of open endedparison. Preblow air of about 3 p.s.i.g. is passed through parison 21during extrusion of the 2 inches of parison and is then terminated bydelay timer 42 switching itself to the on position thereby switchingvalve 44 to cause air to pass through line 49 instead of the normal paththrough 46. While the flow of preblow air is being terminated, thepiston in cylinder 12 is being activated and after termination of theflow of preblow air, the parison is prepinched at a point intermediateits approximate 2 inch length. Pinch bars 1 and 2 are retained in thepinched position for -about one-tenth of a second at which time timedelay 42 times out and switches valve 44 back to its normal positionwhereby air passes through lines 46, 47, and 48. Pinch bars 1 and 2 arethereby retracted and preblow air passes into air delay 54. After abouta two-second del-ay of the air in 54 during which time the parison isextruded to a length of about 4 inches above the prepinched area, thepreblow air is released by 54 and admitted to the interior of theparison.

Reasonable variations and modifications are possible within the scope ofthis disclosure without departing from the spirit and scope thereof.

We claim:

1. Apparatus for prepinching a parison comprising a pair of opposedpinch members which are rotatably carried on at least one gear means andadapted to be carried below a parison forming means and above a moldmeans for molding the parison, at least one gear means for each of saidpinch members being meshed with one another, a separate gear meansmeshed with one of said gear means, and means for moving said separategear means so as to cause rotation of said pinch member gear means andtherefore cause the movement of said pinch members towards and away fromone another.

2. The apparatus according to claim 1 wherein said pinch members areelongate bars carried by two arms extending from either end of each barto a gear so that each bar is supported by two arms each terminated by agear, two gears for each bar being meshed with two gears of the opposingbar, said separate gear means is a rack which is meshed with one gear ofone of said bars, and a pneumatically operated piston rod is connectedto said rack to reciprocably move same.

3. The apparatus according to claim 1 wherein a knockout fiange iscarried on the bottom of at least one of said pinch members in a mannerso that when the pinch members are moved towards one another the flangehits a p0rtion of the molded article that extends out from the mold inthe direction of the pinch members and thereby ejects the molded articlefrom the mold.

4. The apparatus according to claim 1 wherein said pinch members arecoated with polydimethylsilicone.

5. The apparatus according to claim 1 wherein the parison forming meanscarries interiorly thereof a fluid carrying conduit for passing a fluidinto the prepinched parison to preblow same before it is confined in amold and blow molded.

6. The apparatus according to claim 5 wherein the prepinching andpreblowing apparatus is controlled so that no preblowing occurs duringprepinching and for a finite period of time after prepinching by thefollowing: an accumulator means openly connected to and upstream of saidparison forming means; means for filling said accumulator means withmaterial from which the parison is formed; means to move material fromsaid accumulator to form said parison; a first switch means adjacentsaid means for moving material from said accumulator and saidaccumulator itself; a second switch means adjacent said means for movingmaterial from said accumulator but spaced away from said first switchmeans; an actuating means carried by said means for moving material fromsaid accumulator and adapted to actuate said first switch means and saidsecond switch means; means for moving said molds; means operativelyconnecting said first switch means and .said means for moving saidmolds; a valve means operatively connected to the means for moving saidseparate gear means; said valve being adapted to when in a firstposition cause said separate gear means to move said pinch memberstowards one another and when in its normal second position cause saidseparate gear means to move said pinch members away from one another andto cause fluid to pass through said fluid carrying conduit; a first timedelay means operatively connected between said second switch means andsaid valve; a normally closed second v-alve operatively connected tosaid fluid carrying conduit; a third switch means adapted to be actuatedwhen said molds are moved away from one another, said third switch meansbeing operatively connected to said second valve; and an air delay meansdownstream from said second valve.

7. The apparatus according to claim 5 wherein the prepinching andpreblowing apparatus are controlled to prevent preblowing duringprepinching and for a finite period of time after prepinching by thefollowing: a piston carrying accumulator openly connected to andupstream of said parison forming means; a piston rod connected to saidpiston and extending outside said accumulator; means for filling saidaccumulator with material from which the parison is formed; said pistonbeing adapted to be retracted by the force of incoming material fromsaid means for filling said accumulator; means to move said pistonforward against said f-orce of incoming material and force material insaid accumulator through said parison forming means; a first switchmeans adjacent said piston rod and adjacent said accumulator; a secondswitch means adjacent said piston rod but spaced away from .said firstswitch means in the direction of retraction of said piston; andactuating arm carried by said piston rod and adapted to actuate saidfirst switch means when said piston is in about its forwardmost, parisonforming position in said accumulator, and adapted to actuate said secondswitch means when said piston is in about its most retracted,accumulator filling position; means for moving said molds towards andaway from one another; means operatively connecting said first switchmeans and said means for moving said molds so that when said firstswitch means is actuated said molds move towards one another to mold Iaparison; a four-way, spring return, air valve operatively connected toan air operated cylinder containing a piston whose piston rod carriessaid separate gear means; said four-way valve being adapted to when in afirst position pass air into said cylinder to cause said separate gearmeans to move and cause said pinch members to move towards one another;and when in its normal second position to pass air into both saidcylinder to cause said separate gear means to move and cause said pinchmembers to move away from one another and said fluid carrying conduit; afirst time delay means operatively connected to said .second switchmeans and said fourway valve and adapted to upon actuation of saidsecond switch means delay the switching of said four-way valve to saidfirst position for a finite period of time and after said four-way valveis switched to said first position further delay returning said four-wayvalve to its normal second position to allow time for pinching of theparison; a normally closed two-way valve operatively connected to saidfiuid carrying conduit; a third switch means operatively connected tosaid two-way valve and adapted to be actuated by one of said molds whensaid molds are moved away from one another after a parison moldingoperation has been completed, actuation of said third switch meanscausing opening of said normally closed two-way valve; and an air delaymeans that is self-resetting when the air flow therethrough isterminated and that is operatively mounted downstream from said two-wayvalve; said air delay means being adjusted to delay the passage of airinto the parison for a finite period of time sufiicient to allow theformation of a parison of sufficient internal volume to contain said airwithout rupturing.

References Cited UNITED STATES PATENTS 3,217,072 ll/1965 Schaich 18-5 X3,277,223 10/1966 Curto 18-5 X 3,300,556 1/1967 Battenfeld et al. 18-5 XFOREIGN PATENTS 688,997 3/1953 Great Britain.

WILBUR L. MCBAY, Primary Examiner.

U.S. Cl. X.R. 264-98

7. THE APPARATUS ACCORDING TO CLAIM 5 WHEREIN THE PREPINCHING ANDPREBLOWING APPARATUS ARE CONTROLLED TO PREVENT PREBLOWING DURINGPREPINCHING AND FOR A FINITE PERIOD OF TIME AFTER PREPINCHING BY THEFOLLOWING: A PISTON CARRYING ACCUMULATOR OPENLY CONNECTED TO ANDUPSTREAM OF SAID PARISON FORMING MEANS; A PISTON ROD CONNECTED TO SAIDPISTON AND EXTENDING OUTSIDE SAID ACCUMULATOR; MEANS FOR FILLING SAIDACCUMULATOR WITH MATERIAL FROM WHICH THE PARISON IS FORMED; SAID PISTONBEING ADAPTED TO BE RETRACTED BY THE FORCE OF INCOMING MATERIAL FROMSAID MEANS FOR FILLING SAID ACCUMULATOR; MEANS TO MOVE SAID PISTONFORWARD AGAINST SAID FORCE OF INCOMING MATERIAL AND FORCE MATERIAL INSAID ACCUMULATOR THROUGH SAID PARISON FORMING MEANS; A FIRST SWITCHMEANS ADJACENT SAID PISTON ROD AND ADJACENT SAID ACCUMULATOR; A SECONDSWITCH MEANS ADJACENT SAID PISTON ROD BUT SPACED AWAY FROM SAID FIRSTSWITCH MEANS IN THE DIRECTION OF RETRACTION OF SAID PISTON; ANDACTUAATING ARM CARRIED BY SAID PISTON ROD AND ADAPTED TO ACTUATE SAIDFIRST SWITCH MEANS WHEN SAID PISTON IS IN ABOUT ITS FORWARDMOST, PARISONFORMING POSITION IN SAID ACCUMULATOR, AND ADAPTED TO ACTUATE SAID SECONDSWITCH MEANS WHEN SAID PISTON IS IN ABOUT ITS MOST RETRACTED,ACCUMULATOR FILING POSITION; MEANS FOR MOVING SAID MOLDS TOWARDS ANDAWAY FROM ONE ANOTHER; MEANS OPERATIVELY CONNECTING SAID FIRST SWITCHMEANS AND SAID MEANS FOR MOVING SAID MOLDS SO THAT WHEN SAID FIRSTSWITCH MEANS IS ACTUATED SAID MOLDS MOVE TOWARDS ONE ANOTHER TO MOLD APARISON; A FOUR-WAY, SPRING RETURN, AIR VALVE OPERATIVELY CONNECTED TOAN AIR OPERATED CYLINDER CONTAINING A PISTON WHOSE PISTON ROD CARRIESSAID SEPARATE GEAR MEANS; SAID FOUR-WAY VALVE BEING ADAPTED TO WHEN IN AFIRST POSITION PASS AIR INTO SAID CYLINDER TO CAUSE SAID SEPARATE GEARMEANS TO MOVE AND CAUSE SAID PINCH MEMBERS TO MOVE TOWARDS ONE ANOTHER;AND WHEN IN ITS NORMAL SECOND POSITION TO PASS AIR INTO BOTH SAIDCYLINDER TO CAUSE SAID SEPARATE GEAR MEANS TO MOVE AND CAUSE SAID PINCHMEMBERS TO MOVE AWAY FROM ONE ANOTHER AND SAID FLUID CARRYING CONDUIT; AFIRST TIME DELAY MEANS OPERATIVELY CONNECTED TO SAID SECOND SWITCH MEANSAND SAID FOURWAY VALVE AND ADAPTED TO UPON ACTUATION OF SAID SECONDSWITCH MEANS DELAY THE SWITCHING OF SAID FOUR-WAY VALVE TO SAID FIRSTPOSITION FOR A FINITE PERIOD OF TIME AND AFTER SAID FOUR-WAY VALVE ISSWITCHED TO SAID FIRST POSITION FURTHER DELAY RETURNING SAID FOUR-WAYVALVE TO ITS NORMAL SECOND POSITION TO ALLOW TIME FOR PINCHING THEPARISON; A NORMALLY CLOSED TWO-WAY VALVE OPERATIVELY CONNECTED TO SAIDFLUID CARRYING CONDUIT; A THIRD SWITCH MEANS OPERATIVELY CONNECTED TOSAID TWO-WAY VALVE AND ADAPTED TO BE ACTUATED BY ONE OF SAID MOLDS WHENSAID MOLDS ARE MOVED AWAY FROM ONE ANOTHER AFTER A PARISON MOLDINGOPERATION HAS BEEN COMPLETED, ACTUATION OF SAID THIRD SWITCH MEANSCAUSING OPENING OF SAID NORMALLY CLOSED TWO-WAY VALVE; AND AN AIR DELAYMEANS THAT IS SELF-RESETTING WHEN THE AIR FLOW THERETHROUGH ISTERMINATED AND THAT IS OPERATIVELY MOUNTED DOWNSTREAM FROM SAID TWO-WAYVALVE; SAID AIR DELAY MEANS BEING ADJUSTED TO DELAY THE PASSAGE OF AIRINTO THE PARISON FOR A FINITE PERIOD OF TIME SUFFICIENT TO ALLOW THEFORMATION OF A PARISON OF SUFFICIENT INTERNAL VOLUME TO CONTAIN SAID AIRWITHOUT RUPTURING.